inequalities using math node
I used the Node Expressions add-on (available via https://baldingwizard.wixsite.com/blog/node-expressions) to create the nodes from the mathematical expression, using the following expression :
Val1 = abs(y-(9-8*abs(x))) &lt; Threshold, Val2 = and(abs(x)&gt;0.75, abs(x)&lt;1), Combined =Val1 * Val2

This creates two sub-expressions (Val1 which returns 'true' if y is close to '9-8|x|' and Val2 which is true if 0.75 &lt; |x| &lt; 1.0) and a Combined output which is true if both sub-expressions are true.
This produces the following result :

Blend file included